Biological warfare agents if released pose a great harm to mankind. Biological warfare agents including bacterial endospores like Bacillus anthracis, vegetative bacterial cells like Vibrio cholera and viruses like smallpox have been used in the past and will also be used in future military conflicts between nations and terrorists. Particularly, there were several incidents of bioterrorism in the fall of 2001 after the events of September 11, when preparations of Bacillus anthracis were mailed to public and private institutions, leading to 5 deaths and having a profound effect on the national psyche. The cost of decontamination and remediation of these attacks was very high. The main decontamination processes of these anthracis attacks were stripping and fumigation using chlorine dioxide, which is a toxic substance.
Elimination of unwanted microbes in seawater may be very useful in the shipping and fish-farming industries. World coastlines are contaminated by foreign biological species from ships' ballast water, disturbing local ecological systems. For example, copepods, native to Japan, China and Korea, appeared first in the Colombia River in 1990 have now spread to all of the west coast rivers in North America, displacing native copepods. European mussels brought by ships invaded the five great lakes in the US, causing great damage to hydro-electric power plants and factories. According to the US Coast Guard, the US spent more than 1 billion dollars to rectify this situation. In fact, the world sterilization cost of the pollution caused by ballast water is approximately 10 billion dollars annually. The International Maritime Organization decided that ballast water must be sterilized before discharging in order to prevent the spreading of foreign biological species and to protect the local ecological system. The fish-farming industries use various chemicals to kill bacteria, viruses and fungi, and these chemicals can harm fish populations and human. One of the notorious chemicals used in fish-farming industry is Malachite green, a carcinogenic material. Sterilizing unwanted microbes in seawater without the use of toxic chemicals is required.
Ozone is very effective in sterilizing microbes. Ozone after sterilization disintegrates into oxygen without leaving any harmful materials to environment. The difficulties associated with ozone are its finite lifetime in water and efficiency. In this context, properties of ozone in water have been investigated. Particularly, the ozone decay time in water was measured for a broad range of physical parameters including several values of ethanol concentration and different pH values. The increase of ozone decay time by lowering the pH value of the water was observed. It was also noted that the decay time decreases drastically as the ethanol concentration increases.
Assuming that N represents the microbe number in unit volume, the number of microbes killed per unit time and unit volume by acidic ozone water can be represented by
                                                        ⅆ              N                                      ⅆ              t                                =                      -                          N              ⁡                              [                                  α                  ⁢                                                                          ⁢                                      n                                          O                      ⁢                                                                                          ⁢                      3                                                        ⁢                                      exp                    ⁡                                          (                                              -                                                  t                          τ                                                                    )                                                                      ]                                                    ,                            (        1        )            where nO3 is the initial ozone density, and α is the inactivation coefficient of ozone in units of L/(mg·s). Ozone (αnO3) in acidic ozone water in Eq. (1) inactivates the microbes. Integration of Eq. (1) over time t gives the density of microorganisms in terms of time t:
                                          log            ⁡                          (                                                N                  ⁡                                      (                    t                    )                                                                    N                  0                                            )                                =                                    -              0.43                        ⁢            α            ⁢                                                  ⁢                          n                              O                ⁢                                                                  ⁢                3                                      ⁢                          τ              ⁡                              [                                  1                  -                                      exp                    ⁡                                          (                                                                        -                          t                                                /                        τ                                            )                                                                      ]                                                    ,                            (        2        )            where the constant N0 represents the initial density of microorganisms. As can be seen from the theoretical model in Eq. (2), the concentration (nO3) of ozone and its decay time (τ) are the critically important factors on the sterilization. Increase of the ozone decay time (τ) enhances the sterilization effects. The theoretical model developed in Eq. (2) for sterilization of microbes by ozone in water indicates that the main synergic effect of the acidity in water is the increase of the ozone decay time at a low pH value, thereby effectively killing endospores of Bacillus atrophaeus, demonstrating a potential for sterilization of microbes on a large contaminated area in a very short time and reinstating the contaminated environment as free from biological agents.
The purpose of the present invention is to develop a rapid and effective eliminating method of toxic biological warfare agents from large contaminated areas in the event of a release of agents on the environment, civilians or facilities. The acidic ozone water (AOW) can be produced abundantly in various forms like solutions, foams with substances, as well as mist and fog to satisfy a wide variety of operational objectives and can be retrofitted into many existing decontamination apparatus. The ozone in the acidic ozone water decays reasonably fast into oxygen without any trace after the decontamination process. The acidic water after the decontamination process can also be neutralized without any burden to the environment. Therefore, the acidic ozone water may be a good candidate for a mass sterilization of toxic biological warfare agents.
The acidic ozone water was proposed in the U.S. Pat. No. 5,983,909 issued to Oh Eui Yeol et. al. on Nov. 16, 1999. In that invention, an aqueous oxidizing acidic cleaning solution is produced by mixing an acidic solution with ozone water. An aqueous reducing acidic cleaning solution is produced by mixing an acidic solution with hydrogen water. The aqueous cleaning solution has effective cleaning power. Therefore, by selecting an appropriate aqueous cleaning solution according to the types of contaminants adhering to subjects during each manufacturing step, a plurality of types of contaminants can be removed by washing with this aqueous cleaning solution. On the other hand, the present invention makes use of synergic benefits derived from the combination of ozone and acidity in the acidic ozone water with a low pH value for sterilization of microbes instead of cleaning subjects.
The ozone and acidity in the acidic ozone water kill the microbes and then disintegrate into oxygen and ordinary water without leaving any trace of them as time goes by, thereby being harmless to the environment. The acidic ozone water therefore must be used to sterilize the contaminated area as soon as it is produced. This property is beneficial to the environment but limits applications of the acidic ozone water to broad areas because of ozone disintegration. Ozone dissociation in water is initiated by the negative OH ions, whose number increases faster with the pH value of the acidic water. For example, the ozone decay time (τ) in the acidic ozone water with the pH value of 4 is about twice as long than that in ordinary fresh water with a pH value of 7. Therefore, it is much easier for a low pH value to make the ozonated water with high ozone concentration.
The ozone molecules disintegrate into oxygen molecules as they meet the negative OH ions or any other organic contaminants in water. The translational motion of the molecules in the water becomes faster as the water temperature increases. Ozone molecules have a higher chance of meeting the negative OH ions or other contaminants as the water temperature T increases. Accordingly, the ozone decay time τ in the acidic ozone water increases as the water temperature T decreases. The ozone in the acidic ozone water decays slowly if the water temperature is less than 4 degree Celsius. The chilled acidic ozone water preserves its properties long after its creation. The slowly decaying ozone molecules, before their disintegration, in the chilled acidic ozone water have a better chance of meeting and killing microbes.
Ice is the water crystal produced from freezing water. Ozone molecules, the positive hydrogen ions, the negative OH ions, and other contaminants in the acidic ozone ice are embedded inside the ice crystal. The positive hydrogen ions, whose density represents the acidity in the acidic ozone water, cannot move freely in ice, thereby preserving the ice acidity almost permanently. The ozone molecules in the acidic ozone ice are not allowed to meet the negative OH ions or any other contaminants in the ice, so that the ozone decay time τ becomes infinite in the acidic ozone ice. The ozonated ice was proposed in the U.S. Pat. No. 6,506,428 B1 issued to Berge and McClure on Jan. 14, 2003. In that invention, the ozonated ice was made for the disinfections of microbes by melting it as needed. The present invention extends the ozonated water concept in the previous U.S. Pat. No. 6,506,428 B1 to the acidic ozone water. The acidic ozone ice preserves its strong sterilizing-character permanently.
It is therefore an important object of the present invention to enhance the sterilizing strength of the acidic ozone water in order to achieve the elimination of toxic biological warfare agents in the contaminated area by exposing it to the ozone and acidity simultaneously in the acidic ozone water.
Another object of the present invention is to provide synergic benefits derived from the combination of ozone and acidity in the acidic ozone water for the sterilization of microbes on a large surface area contaminated by biological warfare agents.
One other object of the present invention is to provide synergic benefits derived from the combination of ozone and acidity in the acidic seawater for the sterilization of a large amount of seawater in a short time.
One additional object is to overcome the difficulties associated with the ozone decay in the acidic ozone water, and heretofore experienced in achieving efficient and rapid elimination of the toxic biological agents by chilling or freezing the acidic ozone water.
Additional objects, advantages and novel features of the invention will be explained in part in the following description, and will be apparent to those skilled in the following experiment.